Justin Mannheimer, 31, of Inscription House, Arizona, is going to prison for eight years after admitting to sexually assaulting a minor and repeatedly strangling her during a months-long captivity on the Navajo Nation. The sentence, handed down May 20, 2019, by U.S. District Judge Douglas Rayes, includes lifetime supervised release—marking one of the most severe federal crackdowns on violent sexual crimes in the region this year.
Mannheimer pleaded guilty to two federal charges: sexual conduct with a minor and domestic assault by strangling, a felony under federal domestic violence statutes. The crimes occurred between August 1, 2017, and December 14, 2017, inside his home in Inscription House, where he held the underage victim against her will. Authorities say the girl was isolated, controlled, and subjected to repeated sexual and physical abuse during that time.
Both Mannheimer and the victim are enrolled members of the Navajo Nation, and the crimes took place within the reservation’s jurisdiction—placing the case under federal authority due to the Major Crimes Act. The Navajo Nation, plagued by underfunded law enforcement and jurisdictional complexities, relies heavily on federal agencies like the FBI to investigate serious violent offenses, especially those involving minors.
The FBI led the investigation, untangling a pattern of coercion and violence that had gone unreported for months. Prosecutors said evidence showed Mannheimer used intimidation and physical force to maintain control over the victim, cutting her off from family and support systems. The strangulation charges underscore the life-threatening nature of the abuse—highlighting a disturbing trend in domestic violence cases on tribal lands.
Assistant U.S. Attorneys Sharon K. Sexton of the District of Arizona prosecuted the case in Phoenix federal court. In a statement, prosecutors emphasized that crimes of this severity, especially when involving children, will be met with maximum penalties under federal law. “This sentence sends a message: we will pursue justice for victims, no matter how isolated they may be,” said a DOJ spokesperson.
Mannheimer was sentenced under case number CR-18-8037-PCT-DLR and will serve his time in a federal prison, followed by lifetime supervision. The U.S. Attorney’s Office, District of Arizona, released the announcement under number 2019-067_Mannheimer. For ongoing updates, visit www.justice.gov/usao/az or follow @USAO_AZ on Twitter.
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Key Facts
- State: Arizona
- Agency: DOJ USAO
- Category: Sex Crimes
- Source: Official Source ↗
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